Translator


1   // Copyright 2004, 2005 The Apache Software Foundation
2   //
3   // Licensed under the Apache License, Version 2.0 (the "License");
4   // you may not use this file except in compliance with the License.
5   // You may obtain a copy of the License at
6   //
7   //     http://www.apache.org/licenses/LICENSE-2.0
8   //
9   // Unless required by applicable law or agreed to in writing, software
10  // distributed under the License is distributed on an "AS IS" BASIS,
11  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12  // See the License for the specific language governing permissions and
13  // limitations under the License.
14  
15  package org.apache.hivemind.schema;
16  
17  import org.apache.hivemind.Location;
18  import org.apache.hivemind.internal.Module;
19  
20  /**
21   * Object which can translate a string into an object value.  This is used to
22   * translate attribute values (or element content) from strings into
23   * numbers, booleans or other constructs before assigning the final value
24   * to a propery.  Translation occurs after symbol substitution.
25   * 
26   * <p>
27   * Translator classes should have a public constructor that takes no
28   * arguments.  They may optionally have a second constructor
29   * that takes a single string as a parameter.  When the
30   * {@link org.apache.hivemind.parse.DescriptorParser} encounters
31   * a <code>translator</code> of the form 
32   * "<code><i>translator-id</i>,<i>initialization-string</i></code>"
33   * (example: "int,min=0") it will use the second constructor, passing
34   * the initialization string.
35   * 
36   * <p>
37   * Generally, initializion strings are of the form
38   * <code><i>key</i>=<i>value</i>[,<i>key</i>=<i>value</i>]*</code>.
39   * Each initializer has a set of keys it recognizes, other keys are simply
40   * ignored.
41   *
42   * @author Howard Lewis Ship
43   */
44  public interface Translator
45  {
46      /**
47       * Invoked by a {@link org.apache.hivemind.schema.Rule} 
48       * to translate an inputValue into an appropriate object.
49       * Substitution symbols will already have been expanded before this method is
50       * invoked.
51       * 
52       * @param contributingModule the module from which the input value originates
53       * @param propertyType the type of the property to be assigned by this translator; smart translators may
54       * be able to automatically convert from string to the correct type
55       * @param inputValue the value to be translated, either an attribute value or the content of the element
56       * @param location the location of the inputValue; used to set the location of created objects,
57       * or when reporting errors
58       */
59      public Object   translate(
60          Module contributingModule,
61          Class   propertyType,
62          String   inputValue,
63          Location location);
64  }
65
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